/Engine/Source/Editor/UnrealEd/Classes/Editor/UnrealEdEngine.h
Checks the state of the selected actors and notifies the user of any potentially unknown destructive actions which may occur as the result of deleting the selected actors. In some cases, displays a prompt to the user to allow the user to choose whether to abort the deletion.
false to allow the selected actors to be deleted, true if the selected actors should not be deleted.
virtual bool ShouldAbortActorDeletion() const